Synchronous Rectifier Post Regulation for DC-DC Converters
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Solution Overview
Problem
Existing DC-to-DC converters face limitations in gain bandwidth and transient response due to transformer magnetic materials and designs, which restrict switching frequencies and add losses with additional conversion stages for post regulation.
Innovation Solution
The use of existing synchronous rectifiers in DC-to-DC converters for post regulation, adjusting parameters such as on-resistance or effective average voltage drop through linear or PWM methods to achieve target outputs without additional conversion stages, allowing independent operation from the main control loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional conversion stages (linear regulators or PWM buck regulators) are added for post regulation, then load regulation and transient response are improved, but device complexity and energy losses increase
Solution Approach 1:
The synchronous rectifier is designed to perform dual functions: primary rectification during normal operation and post-regulation during transient conditions. By making the rectifier universal, the patent eliminates the need for separate post-regulation stages, thereby reducing device complexity while maintaining improved load regulation and transient response characteristics
2Speed
If additional conversion stages (linear regulators or PWM buck regulators) are added for post regulation, then transient response is improved, but energy losses increase
Solution Approach 1:
The synchronous rectifier performs both rectification and post-regulation functions, eliminating energy losses associated with additional conversion stages
Solution Approach 2:
The patent converts the inherent on-resistance of the synchronous rectifier, which normally represents a loss, into a beneficial regulating element during transient conditions. By controlling the rectifier's conduction state, the previously harmful resistance becomes a useful tool for fast transient response without additional energy losses
3Speed
If switching frequency is increased to improve transient response, then speed is improved, but losses due to core losses and leakage inductance increase
Solution Approach 1:
The patent dynamically controls the synchronous rectifier's operation based on transient conditions. During load transients, the rectifier is actively controlled to provide fast response, while during steady-state operation, it operates in its optimal rectification mode. This dynamic adaptation allows fast transient response without permanently increasing switching frequency and associated core losses
4Speed
If switching frequency is increased to improve transient response, then speed is improved, but losses due to leakage inductance increase
Solution Approach 1:
The synchronous rectifier provides dynamic control during transient conditions, enabling fast response without permanently increasing switching frequency. The rectifier's active control during transients compensates for leakage inductance effects without requiring continuous high-frequency switching, thereby maintaining low leakage inductance losses
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances load regulation, reduces output voltage ripple, and improves transient response by avoiding the limitations of the main control loop, while maintaining high efficiency and power density.
Implementation Method 1
adjusting parameters such as on-resistance or effective average voltage drop through linear or PWM methods
Data Source
AI summary
Methods and apparatus for regulating a synchronous rectifier DC-to-DC converter by adjusting one or more existing synchronous rectifiers in the converter are provided. By regulating an existing synchronous rectifier, the rectifier may function as a modulator for post regulation over a limited range of output voltages suitable for load regulation, without introducing an additional conversion stage for post regulation, which typically decreases efficiency and power density. Independent post regulation of an existing synchronous rectifier may improve the load regulation, reduce output voltage ripple and improve the transient response of the converter. By operating independently from the main control loop, post regulation may most likely avoid the limitations of the main control loop, such as limited gain bandwidth and a relatively slow transient response. Such post regulation may be added to isolated or non-isolated switched-mode power supplies, such as forward or buck converters.